1. Technical Field
The present disclosure relates to methods of manufacturing reference sample substrates for analyzing metal contamination levels. More particularly, the present disclosure relate to methods of manufacturing reference sample substrates employed for analyzing metal contamination sources remaining on semiconductor substrates.
2. Description of the Related Art
As various contaminants may have a direct effect on the production yield of semiconductor devices, contaminants should be strictly controlled in current semiconductor manufacturing processes. Particularly, among the various contaminants, metallic contaminants may have a direct effect on the electrical reliability of a semiconductor device and thus these metallic contaminants should be more thoroughly controlled in the semiconductor manufacturing processes. For example, a metallic contamination source such as iron (Fe) and/or nickel (Ni) remaining on a semiconductor substrate is typically measured and analyzed during semiconductor manufacturing processes.
In an analysis of the metallic contamination source on a surface of the semiconductor substrate, an analysis apparatus such as a secondary ion mass spectrometry (SIMS) or a total X-ray reflection fluorescence (TXRF) is currently employed because of the minute amounts of the metal contamination source which may remain on the surface of the semiconductor substrate. When the metallic contamination source is analyzed using such an analysis apparatus, the reference sample substrate is required because the analysis of the metallic contamination source is usually performed as a quantitative analysis and a relative analysis.
The reference sample substrate is typically manufactured by at least one of the conventional methods set forth below.
For example, a reference sample substrate may be manufactured by a conventional method in which a solution including a predetermined content of metal impurities as a metal contamination source is dropped on a semiconductor substrate, and then the semiconductor wafer is dried to obtain the reference sample substrate. A reference sample substrate may also prepared by another conventional method that includes immersing a semiconductor substrate into a solution having a predetermined content of metal impurities as a metal contamination source, and drying the immersed semiconductor wafer. Additionally, the reference sample substrate may be manufactured by still another conventional method described in Japanese Patent Laid-Open Publication No. 1990-156636. In the method described in the Japanese Patent Laid-Open Publication No. 1990-156636, the reference sample substrate is manufactured by coating a soluble metallic salt as a metal contamination source remaining on a semiconductor substrate. Furthermore, Japanese Patent Laid-Open Publication No. 1994-249764 describes still another conventional method of manufacturing a reference sample substrate, which includes immersing a semiconductor substrate into an alkaline peroxide solution including a predetermined content of metal impurities as a metal contamination source, and rinsing the immersed semiconductor substrate using pure water.
When the reference sample substrate is prepared by dropping the solution having the predetermined content of the metal impurities onto the semiconductor substrate or immersing the semiconductor substrate into the solution having the predetermined content of the metal impurities, the metal contamination source may not be uniformly distributed on an entire surface of the reference sample substrate. Additionally, the metal impurities may not be uniformly distributed at desired portions of the semiconductor substrate because the semiconductor substrate has a relatively rough surface wafer and the drying process is irregularly performed about the semiconductor substrate. Thus, the total amounts of the metal impurities in reference sample substrates may differ from one another.
Moreover, when the reference sample substrate is obtained by coating the soluble metallic salt on the semiconductor substrate, the metal impurities may not be positioned at desired portions of the reference sample substrate although the metal impurities may be uniformly distributed on the reference sample substrate. Further, the total amounts of the metal impurities in the reference sample substrates may be different from one another because the compositions of the soluble metallic salts may not be readily controlled, and the semiconductor substrates may have relatively irregular surfaces.
When the reference sample substrate is manufactured by rinsing the semiconductor substrate after immersing the semiconductor wafer into the alkaline peroxide solution including the predetermined content of the metal impurities, the metal impurities may be uniformly distributed at desired portions of the reference sample substrate, and the total amounts of the metal impurities in the reference sample substrates may be substantially the same as one another. However, a thin film containing the metal impurities may still not be properly formed on the semiconductor substrate so that the thickness of the thin film containing the metal impurities on the reference sample substrate may not be varied as desired. Particularly, the reference sample substrate may not include the metal impurities with a high concentration above about 1×1E13 atoma/cm2.
Furthermore, when an analysis apparatus such as the SIMS or the TXRF is employed for analyzing metal contamination levels of the conventional reference sample substrates manufactured by the above-described conventional methods, the reliability and reproductivity of data concerning the metal contamination levels may be deteriorated because the metal impurities may be irregularly distributed on the reference sample substrates and the metal impurities may not be positioned at the desired portions of the reference sample substrates. Additionally, various data relating the metal contamination levels may not be sufficiently ensured because the reference sample substrates may not have various thin films containing the metal impurities.